In instances where it is desired to convey dry, powdered and/or granular products by an air stream from a place of storage to a machine or like destination in a processing line where the product is used, it is oftentimes necessary to purge the pneumatic conveying system so that the dry, powdered and/or granular products are removed from the conveying system before the air stream is shut off. If the material is not so removed from the conveying system by the time the air stream is shut off, the material will settle within the conveying system and eventually plug the system and/or render its conveying effectiveness less than desired. Thus, conventional valves have been provided in the conveying system to block the flow of dry, powdered and granular product into the conveying system while simultaneously allowing a gas to enter the conveying system for purposes of purging the system. Since material exists in the system from the valve back to the storage device, it is oftentimes difficult to monitor the precise volume of material that may be present in this section of the conveying system. In some instances, the quantity of material so located in this particular section negatively impacts upon the ability of the pneumatic conveying system to appropriately convey the material again after it has settled in the conveying system.
Accordingly, it is an object of this invention to provide a single unit device for adjustably metering the volume of dry, powdered and/or granular product delivered to a vacuum type, pneumatic conveying system and for rendering the product entrained in a gas stream flowing into the conduit system to facilitate conveyance of the entrained product from a place of storage to a machine or like destination in a processing line where the product is to be used.
It is a further object of this invention to provide a single unit device, as aforesaid, which is easy to operate for purposes of controlling variable quantities of product to be delivered to the gas stream to thereby allow for an optimization of the product to gas ratio in the conduit system.
It is a further object of this invention to provide a single unit device, as aforesaid, which is self-cleaning when adapted to vacuum type, pneumatic conveying systems having a purge cycle.
It is a further object of this invention to provide a single unit device, as aforesaid, which has the ability to accommodate differing materials under wholly separate operating conditions and without necessitating a replacement of any of the components in the system.
It is a further object of the invention to provide a single unit device, as aforesaid, wherein the adjustment required to accommodate product of different granular size can be made easily and with a minimum of difficulty.
It is a further object of this invention to provide a single unit device, as aforesaid, wherein the device is adapted to be mounted on existing hopper constructions in the field.